Circuit arrangement

Abstract

A circuit arrangement (1), a detection circuit (50, 70) and an LED driver circuit (100, 110) is disclosed for operating at least one lighting unit, such as an LED unit, with a phase-cut operating voltage. The circuit arrangement (1) comprising at least an input (6) for receiving a phase-cut operating voltage from said power supply and / or an output (7) for connection to said at least one lighting unit and a pulse injection circuit, configured to determine a phase-cut operation of said power supply and to draw a current pulse from said power supply within a delay time between 200-700 μs after said phase-cut operation to provide a stable operation of said LED unit with the phase-cut power supply. The detection circuit (50,70) comprises at least an input (6) for receiving a phase-cut operating voltage from said power supply and a lamp compatibility detector (52, 72), configured to determine the presence of a parallel lamp (57), connected in parallel with the detection circuit (50, 70) to said phase-cut power supply during operation and to provide a compatibility signal to a LED driver circuit (100, 110) corresponding to the determination of said parallel lamp (57), so that said driver circuit (100, 110) is set between a normal operating mode and a compatibility mode in dependence of the presence of said parallel lamp (57).

Description

TECHNICAL FIELD[0001]The present invention relates to the field of lighting and in particular to a circuit arrangement for operating a lighting unit with a phase-cut power supply, an LED lamp, a lighting system and a method of operating a lighting unit.BACKGROUND ART[0002]Today, LED-based lighting units are being used for many applications. The low power consumption and long lifetime of LEDs make them a very useful alternative to conventional light sources like incandescent lamps or light tubes. Hence, not only new-designed lighting equipment often utilizes LEDs, but in many markets LED products are being used to replace other light-sources like incandescent or halogen light sources, for instance. These so-called retrofit products have to be compatible with existing lighting / power supply systems.[0003]In many lighting system topologies, dimmed light is needed. In the latter case, a phase-cut power supply / dimmer typically is placed between the lamp and mains. Here, the time evolution...

AI Technical Summary

Benefits of technology

The present invention aims to improve the stability and reduce flicker in a configuration where multiple lamps are connected in parallel to a phase-cut power supply, i.e. a dimmer. The invention achieves this by determining a specific type of lamp that is causing a dimmer edge in both positive and negative half-cycles. This allows for a reliable identification of this lamp type. By drawing a current pulse from the power supply within a delay time after a phase-cut operation, the invention significantly increases the stability of the operation and reduces flicker in the output light.

Problems solved by technology

On its turn this oscillation may cause “early disconnect” of a TRIAC when a phase-cut dimmer is used to provide operating power to the lamps.

Here, the early interruption of energy delivery to the lamp with (intended) wide conduction interval may cause one of the following failures, resulting in an unacceptable light output and / or optical flicker: “early disconnect” of dimmer (especially random or not identical for all lamps and / or at each half cycle), fluctuations in floating (operating) voltage, jitter of edge position, failure of zero-crossing detection mechanism and disappearance of floating (operating) voltage at the lamps.

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